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What Are G9 Halogen Bulbs?

By Jay Leone
Updated May 16, 2024
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G9 halogen bulbs are light bulbs that have looped metal prongs instead of screw-in bases. They come in a variety of sizes and wattage ratings and can be used in many different settings, but are often most popular in desk lamps, accent lights, and small appliances. These sorts of bulbs tend to be very efficient and can be quite long lasting, but they can also get very hot very quickly. Users normally have to be careful when touching them, and they shouldn’t be used in close proximity to paper, fabric, or upholstery because of the heightened risk of fire.

How They Look

The easiest way for a person to identify a G9 halogen bulb is by looking at its base. Most standard bulbs for lamps and home fixtures have what is known as an “Edison” screw socket, which is a round, ridged metal pin or protrusion that physically screws into a base. Halogen lamps in the G9 series don’t have this. Instead, they have two looped prongs of thin metal that sometimes look like stiff wires. These prongs connect and click into halogen fixtures.

The bulbs themselves can come in a variety of different sizes and styles, though most tend to be long and somewhat thin. They are often available in either a clear or frosted finish. In most cases they’re pretty small, too; with the exception of some bulbs intended for industrial use, most will fit comfortably in the palm of the hand.

How They Work

G9 bulbs operate in the same way as almost all other halogen bulbs. These typically feature a tungsten filament and a fill gas that contains traces of iodine or another halogen. The tungsten filaments last longer than they do in incandescent bulbs because of the “halogen cycle.” When the metal evaporates from the heat within the bulb, the halogen causes it to redeposit on the filament. Halogen bulbs must reach external temperatures of at least 250°F (121°C) for the halogen cycle to take place.

It is because of the halogen cycle that the average halogen bulb lasts several times longer than an incandescent bulb. Although they usually burn hotter than incandescent lights, they are also more efficient. G9 bulbs are usually designed to last for anywhere from 2,000 to 6,000 hours of active use.

Halogen bulbs with this type of base are designed to operate under 120-130 volts of electricity, and they are usually available in a wide wattage rage. A higher wattage is equal to a higher initial lumen output. The average 20-watt G9 bulb provides a 170 initial lumen output, while 40-watt bulbs offer about a 600 initial lumen output, and 60-watt bulbs provide an 830 initial lumen output. A 75-watt G9 bulb is capable of producing about a 1,400 initial lumen output. This is about the same amount of light as an incandescent bulb of the same wattage.

Common Uses

Halogen lights can be used in many practical applications, and the G9 halogen bulb system is often ideal for desk pendant lighting and accent lighting. It is also often used in desk lamps and under-cabinet illumination, as well as in small consumer appliances like book lights and makeup mirrors.

Safety Precautions

One of the reasons halogen bulbs illuminate so brightly is because they operate at extremely high temperatures. Consumers should avoid touching these sorts of bulbs directly with their bare skin to avoid potentially serious burns. Also, the oils on skin can penetrate the semi-permeable glass of these bulbs, which can compromise their effectiveness over time. Any grease or oils transferred to the surface of a halogen bulb can be removed with alcohol that has been slightly diluted in water.

There is also an increased risk of fire. People are usually advised to keep their G9 halogen lamps away from papers or other dry materials, and bulbs that are mounted underneath counters should be monitored to ensure both that they are properly installed and that there is enough clearance between their surface and the surface of cabinets or counter tops to avoid the risk of combustion. The bulbs get hot enough that they can ignite things around them, which can be very serious and even deadly.

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Discussion Comments
By anon954139 — On May 30, 2014

LED flood lights are becoming more popular, especially in Germany and other countries as they have a long life and offer the best return on the investment.

You can also check out GU10 LED Lampen - LED bulbs by Lumenstar based in Germany. They offer the best quality of LED light bulbs.

By anon349132 — On Sep 23, 2013

Can a standard 25W G9 Halogen lamp be used in an oven?

By browncoat — On Nov 09, 2011

I know that halogen bulbs are sometimes used in aquarium setups. Including G9 bulbs, I think.

You have to make sure to get the kind of bulbs which are suited for your particular kind of aquarium though, as a normal halogen isn't powerful enough for a reef aquarium.

If you are growing fresh water plants, generally it will be all right, but for a reef you'd need, at a minimum, to get Very High Output bulbs.

That's because the light needs to be able to penetrate the water deeply enough for the corals to use it for photosynthesis.

And you might also need to mix in a few blue bulbs, as the halogens tend towards the red end of the light spectrum.

Lighting for reef aquariums seems to be quite complicated. I've been studying it for a while, trying to decide what to get and the amount of options is quite intimidating.

By umbra21 — On Nov 08, 2011

@KoiwiGal - They might not be used in our standard light sockets, but halogens are used for quite a few other things. The lights on your car for example. In fact when they were first installed in cars, they were so bright that they would cause accidents.

That's why they came up with a way of shielding them, so they weren't so very bright they were blinding oncoming drivers.

They also get used as flood lights for sports fields and things like that, although LED lights are starting to become more popular, since they last longer and they aren't so dangerously hot. I think they might be more efficient with energy as well.

By KoiwiGal — On Nov 07, 2011

The coolest thing about halogen bulbs is that they were originally invented for the wingtips of airplanes. They aren't very efficient, but they are very bright and were used in 707s as navigation lights.

They were invented to combat the fact that previous kinds of bulbs would quickly darken, because they would get a film coating the inside of the bulb.

Halogen bulbs don't get the film, but they need to be very hot in order to work, which is one reason they were never very popular as a general kind of bulb.

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